This invention relates to insulating covers for electrical equipment and, more particularly, to insulating covers to prevent or reduce power interruptions on distribution utility lines caused when wildlife bridge high voltage circuits.
Power quality has become an important issue with utility companies as customers increasingly demand uninterrupted power feeding their establishments. Increased use of computers and digital equipment has significantly increased expectations for continuous power, free of momentary interruptions. The leading cause of power interruptions on distribution utility lines is bridging of high voltage circuits by wildlife. Birds and squirrels are the most frequent offenders. To reduce the outages associated with wildlife perching or sitting on distribution transformers, molded covers of various styles, made of insulating materials, are being utilized on the high voltage connections to prevent the animals from making contact with these connections.
Many transformers have lightning arresters mounted to the side of the transformer tanks. These arresters typically mount to a metal bracket that is bolted to the transformer tank. Although these arresters typically employ a small wildlife cover, it is generally not effective in preventing wildlife from making contact with the energized parts. A common cause of outages is wildlife perching near the arrester bracket and mounting bracket at ground potential and making contact with the high voltage connection on the arrester. The animal, being electrically conductive, initiates a high current electrical arc to the arrester bracket. This typically results in operation of high current protective devices, such as fuses, which disconnect the transformer from the circuit, thereby interrupting power to the customers being fed from this transformer. Often the heat of the electrical arc damages the transformer and or the arrester. The power to the customer is not restored until a service lineman becomes available to replace the damaged equipment.
To prevent these types of outages, utilities have attempted to insulate the mounting point of these arresters so that animals perching in this area are effectively insulated from ground potential to prevent current flow when they make contact with the high voltage connection on the arrester. Utilities have tried using things such as tape, insulating putty, and molded bolt caps in an attempt to insulate this perching point. None have proven truly effective over the long term.